1. Field of the invention
The present invention relates generally to radio receivers and, more particularly, to a radio receiver by which a listener can readily select a target broadcasting station without knowing the frequency of the broadcasting station or its broadcasting time.
2. Description of the Prior Art
Overseas broadcasts are generally performed by use of a shortwave band. In some broadcasting stations, the broadcasting schedule is determined as shown, for example, in FIG. 1. In FIG. 1, hatched portions represent time periods in which the broadcasts are performed. In this example, during the time period T1, two broadcast waves of frequencies f1 and f2 are employed to broadcast the same radio program (the same content); during the time period T2, the broadcast wave of frequency f2 is employed to broadcast the next radio program; and during the time period T3, the broadcast wave of frequency f3 is employed to broadcast a different radio program. Accordingly, when a user wants to listen to the radio program transmitted during the time period T1, the user can select one optimum frequency of the frequencies f1 and f2 and can listen to the selected radio program. Further, during the time periods T2 and T3, the listener can selectively listen to a desired one of the radio programs because different radio programs are broadcast using the broadcast waves of frequencies f2 and f3 during the time periods T2 and T3.
According to the above-mentioned radio broadcasting system in which a certain broadcasting station performs radio broadcasts in different time periods by utilizing a plurality of frequencies, dedicated listeners or those with some expertise in the use of shortwave radio can enjoy the benefits of such radio broadcasting system because they remember the broadcast frequencies and broadcast times on the basis of their experience. It is, however, frequently observed that beginners or ordinary listeners are perplexed by the operation of shortwave radio broadcasting stations so that they cannot listen to the desired radio broadcast without difficulty because they are requested to make a channel selection on the basis of the broadcast time schedule shown in FIG. 1. Further, the manufacturers that make radio receivers for receiving overseas radio broadcasts must prepare similar broadcast time schedules for the convenience of those who buy and use the radio receivers.